Answer:
False.
Step-by-step explanation:
This depends on what historical period you are talking about, but typically there are still negotiations between individual countries, though it may not be at the globalization level as today, in comparison. All countries, while trying to expand and become powerful, also want to obtain allies when possible, who can act as security for trade deals, and provide military and traditional aid to the host country when needed. So in a sense, strong nationalism does not make it "impossible" to negotiate with other countries. It may make it harder to obtain allies and and deals with other countries, but in no sense does it become impossible.
If you want to learn more about this topic, do be sure to check out Nationalism as a whole, and the geopolitical climate in Europe historically.
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