Does filing a patent in one country mean the invention is protected only in that country?
You need a patent issued by every country in which you want to enforce it, although there is a European Treaty for a limited number of countries. In most countries you can file a Patent Cooperation Treaty (PCT) application and, for a per-country fee, reserve the right to file a national patent in the future (for a limited time), but you typically have to “convert” your PCT into a national application in EACH country before it gets issued (and enforceable) in that country. So, if you have only a US patent, someone in Spain could, in theory, make, use, sell your invented product and export it to anywhere except the United States, without infringing your US patent.
