Which countries would pose an issue for a PCT filling if my PPA doesn't have a claim?
None (in principle).
Priority is governed by the Paris Convention (1883).
Article 4(1) of this provides:
Any person who has duly filed an application for a patent … shall enjoy, for the purpose of filing in the other countries, a right of priority during the periods hereinafter fixed.
This period is 1 year for patents (Article 4(C)(1)). So the question is: is filing a provisional patent application "duly filing an application for a patent"?
This is clarified by Article 4(2):
Any filing that is equivalent to a regular national filing under the domestic legislation of any country of the Union … shall be recognized as giving rise to the right of priority.
Thus the question is clarifed: is a provisional patent application equivalent to a "regular national filing" under US law?
A "regular national filing" is defined in Article 4(3):
By a regular national filing is meant any filing that is adequate to establish the date on which the application was filed in the country concerned, whatever may be the subsequent fate of the application.
In the US, a provisional patent application is adequate to establish the date on which the application was filed in the US. Indeed, that is entirely the purpose of the provisional. This is the case whether the provisional was filed with claims or not.
Thus, since a provisional patent application is a regular national filing, it gives rise to a right of priority under the Paris Convention.
So any country which (properly) implements the Paris Convention (which is basically every country in the world) would recognise a US provisional patent application as being suitable as a priority document, regardless of whether the provisional has claims.
However, just because a provisional can support priority does not mean that it does support priority. The provisional still needs to be properly drafted, and should probably be, in substance, the same as a non-provisional. Otherwise, the applicant runs the risk of having an insufficient disclosure to properly support the claims of a later filing.
This is the key reason for including claims in a provisional. If you have a claim in the provisional, then you certainly can support the earlier priority to the same claim in a later filing. If you do not have claims in the provisional, you better be careful that your description is good enough to add them later.