Of course I believe you about your intent. But intent isn't enough. "Welcome to X" is a dismissive phrase that belittles someone while purporting to teach them the obvious about a topic. When the topic is "your country at war", that's extremely provocative and presumptuous.

Anyhow, it's clear you didn't mean it that way and it needn't be a big deal. The big-deal aspect is not one phrase in one individual comment—it's the tendency of humans to become mobs when emotions get activated. That, unfortunately, has been displaying itself a lot here lately.