What has kept Islamic Republic of Iran intact over four decades?

Since the end of WWII, the United States has conducted coups against many nations, including Iran in 1953. The US involvement in toppling Shah in 1953 has been confirmed by unclassified CIA documents. After the revolution in 1979, the US and its allies have been making efforts to topple the regime in Islamic Republic of Iran by establishing and supporting various rebel factions within the country, but all in vain.   

It may be worth probing the factors that have kept the regime intact. These include:

1. Since 1979, the US has become increasingly hostile, causing the general population of Iran to become united in support of the regime. The biggest evidence came recently at the funeral of General Soleimani inside and outside Iran.
2. Iranians are concerned that the US support might bring a regime change that could be worse than the present regime.
3. The current regime has successfully created a semi-welfare state by subsidizing basic necessities, and lately providing free medical insurance to all, a situation that does not exist even in the US.
4. The US threats including a steady increase of sanctions, as economic terrorism have had a direct impact on ordinary Iranians.
5. The US pressure on Iranians to topple the present regime is based on the recent US history of regime changes in many countries, specifically in the Middle East, Central and South America.
6. Trump’s maximum pressure on Iran via sanctions has had a significant impact on ordinary Iranians to remain united.
7. Iranians as well as rest of the world understand that western democracy is based on wealth and is not true democracy.    

Strategic Planning of the incumbent regime moved on many fronts to thwart the US, which are:

1-      Going to Syria and defeating US-created ISIS and elements backed by the west, which include, defeat of ISIS in Syria and containment of devastation in Iraq, Libya and Syria.

2-      Policies and the ability to produce defensive and offensive weapons have made the prospect of a US invasion costly.

3-      Development of strategic alliances with Russia and China, with their UN veto power has effectively made overt US aggression illegal.

4-      Iranian regime making a major strategic shift to the balance of world power in favor of Iran, Russia, and China, against other western imperialists.

5-      In June 2019 Iran surprised the world by shooting down a US drone in the Persian Gulf to which there was no US military response.

6-      In late December 2019 IRI conducted military exercises with Russia and China in the Gulf of Oman.

7-      On January 3, 2020 the US assassinated General Soleimani, an act condemned around the world. Following that action, Iran labeled the Pentagon a terrorist organization and US a terrorist state.

8-      The most important strategic achievement of Iran was its response to that killing, shooting 22 missiles into two US military bases in Iraq, again without a US response.

9-      Iran developed a policy of changing US assets into liabilities; also showed that the sole purpose of US weapons has been to increase corporate profit, not for defense.

10-   The US attempts to force Iraqi’s PM to resign, by suggesting he and his defense minister could be killed, failed when the PM refused and made it public, exposing the US as terrorist

Iranians have been gradually uniting as the government counters US provocations, sanctions, sustained hostility, aggression, and existential threats against them. Recently, they have been more critical of the US. There is general support to major strategic achievements including defeating ISIS in Syria and Iraq, and their strategic alliances with the emerging world powers of China and Russia.

Most importantly, the regime has prevented US from invading Iran, made history and changed the world balance of power against US aggression, hopefully moving toward a more peaceful and safer world.