You are confusing two different things.
First is that when US regime prints money out of thin air, they can use it to purchase "real things" from other countries. That is essentially exporting the inflation to those countries. Which means it doesn't matter if the country is developed, developing or under developed. The less they've dedollarised the more they'll be affected by that exported inflation.

Second is the fact that if the local fiat is being dumped, it is partly because of the local non stop printing of that fiat.
Additionally, the exchange rate being low actually means that country CAN compete in the global market and crush others. Why do you think China manipulates its own currency's exchange rate and keeps it down? That is how China became the strongest economy!

So if a certain country has a tough time competing in the global market, the problem is somewhere else. Like in the local economic infrastructure such as industries that even under developed countries have. The focus has to be shifted there and production should increase. That way the lower exchange rate is actually a great thing to have.