The .ASIA proposed TLD falls into a distinct category from traditional classes of TLDs: the gTLDs grouped by type of entity or site, and the ccTLDs that are country-specific. Rather, it is intended to serve a geographical region that is not a single country. However, there are actually other TLDs of this nature that have managed to slip in. Most notably, the .EU domain which is under development will be a regional domain for Europe, implemented as a pseudo-country-code (kind of appropriate given that the European Union acts like a pseudo-country, with its own legislature and currency, even though its component states remain independent nations in their own regard unlike the states of the USA). But there are other ccTLDs that aren't actually countries; Antarctica has .AQ, the Palestinian Authority has .PS, and some territories and possessions of other countries have separate ccTLDs like .PR for Puerto Rico. (.UM for the U.S. minor outlying islands is an odd case in that it doesn't seem to be a specific political or geographical entity, but rather a grab-bag of whatever offshore dependencies of the United States don't rate their own codes.)
Rather than try for another pseudo-country-code, Asia is instead requesting a pseudo-gTLD, even though their intended use isn't globally generic. Granted, there are a few historically grandfathered TLDs that are geographically limited: .GOV and .MIL are US-specific, and really ought to have been logically placed within .US; and .EDU presently maintains a US-only policy (for no defensible reason, in my opinion; it hasn't even been consistently followed in the past, as there are some foreign .EDU registrations). But is it a desirable thing to create more geographically-limited domains that aren't ccTLDs? Perhaps... if there is a large group of people, companies, and organizations in Asia that really want to identify themselves as Asian rather than specifically by their particular country (and they wish to do so using the Latin alphabet rather than one of their own writing systems), then maybe there's a purpose for this TLD. But once it's granted, fairness demands that other similar proposals be accepted when made, for other regional TLDs like .AFRICA.
Of the current bunch of applications, .CAT also falls in the category of regional TLDs, given that it's for the Catalan region. This, however, is a region contained within the country of Spain rather than a transnational one, so the question comes up of whether that one might better be placed within the .ES country code. The same issue does not come up for .ASIA, since it encompasses a number of countries.
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