What is an example of a country compelled by a larger neighbor to maintain a certain political system

During the 1960s the United States sought to prevent communist influence from rising in Vietnam so the U. S. sought to prop up a political order supportive of the U. S.' goals in that region. Additionally U. S. military forces invaded Vietnam in order to prevent the rise of a communist government in Vietnam out of fear that the Soviet Union would gain more influence in South East Asia.