Which countries has China invaded in the past few decades?
Modern China, like Russia, but unlike other autocracies such as Cuba or Saudi Arabia, is a revisionist power - https://en.wikipedia.org/wiki/Revisionist_state
Their publicly broadcasted intention is to change the status quo, forcefully if needed. That's a euphemism for invading Taiwan. They keep saying it, over and over. Beyond that, there's a militarism, nationalism and irredentism that permeates Xi's leadership and the culture he has created in his country, which did not exist to the same extent under Deng. The confluence of such factors have historically been a bad omen.
This does not mean that the US should start a war with China. It means the US should pivot its focus to Asia and continue the policy of containment, which is a maintenance of the peaceful status quo through a combination of sticks and carrots. It means the US should be aware that there is a rival there who may start a war on their own terms and on their own schedule when they believe they are capable of defeating the US.
China has been fairly quiet and well behaved since 1980, but it is current quite publicly talking forcefully reintegrating Taiwan and has had continuous naval disputes in the South China Sea.
If we are talking about colonialism, “China” is a land empire that has absolutely dominated its neighbors and often conquered them. Making an apples to apples comparison to European colonialism isn’t very useful and I don’t pretend to know details, but historical China has plenty of expansionist and domineering episodes.
Well, all of their neighbors for starters.
If we include sending warships to violate maritime sovereignty under that definition, we can add dozens more in Asia and South America.