That will not have a very big effect. However, something like USA banning bitcoins can have huge short term effect. In the long term, crypto will still keep growing. Look at the ban by China which is a major economy in the world. Even after that bitcoin prices have grown at good rates.
You’re right because a lot of bitcoin investors reside in the USA and those who might not be in USA be worried of other countries following suit which could cause a significant drop of price but it will be soon forgotten and the price of bitcoin will go back to its usual trending.
I doubt other countries, let’s say third world ones with not much bitcoin enthusiasts in, would affect the price if they were to ban bitcoin but it would certainly upset some investors that are citizens of that country.
Don't forget that the United States is the financial center of the world and their financial markets account for nearly 50% of the global financial market capitalization. It can be said that the influence of the United States is completely different and much larger than that of China in the market. So a ban from the US would cause the whole market to crash and I am not optimistic if that happens. Not to mention, other countries may not follow China but they will probably follow the US and there will be a worldwide ban if the US bans Bitcoin.
This is the worst case scenario for bitcoin but we can be sure that it will not happen as the US government will face backlash before the ban is enacted. To ban bitcoin, they need to pass a vote in parliament and get presidential approval, which is not as easy as in China.