Vaishnavi Prabhushankar
American government restricted its citizens to visit North Koreabecause oh North KOrea's “serious and mounting risk of arrest and long-term detention.”
The US government restricted the visit to Cuba with 12 approved categories for its citizens.
The unfriendly relationship between the governments of US and Iran, getting a visa, and officially sanctioned host are the reasons why it is little dangerous for Americans even for visit.
Americans require an official government letter of invitation in order to obtain a visa for Turkmenistan; if you come without one, you risk being detained at the airport until you arrange to leave the country.
US nationals must obtain a letter of invitation in order to travel to Russia, and tourist visas can only be obtained for stays of up to 30 days. If you unintentionally overstay your visa, you will need to obtain a new one before you may depart the country.
All females and children, even U.S. citizens, may need a male guardian's approval to leave the nation. You must declare any amount over $16,000 USD as a currency restriction for entry or exit of the kingdom.
U.S. citizens may be detained without access to consular services or knowledge of their alleged offense while visiting or residing in the PRC, including the Special Administrative Regions of Hong Kong and Macau.