No, of course it is not. But one could be lead to believe so, looking at the list of projects carried out by an organization that donates shoes to poor children. Besides Cambodia, Laos, Nicaragua and Timor-Leste, they have a project in the EU member state Romania.
Admittedly, some of the slums here really look like third-world places.
The Happy Hermit 
If we use “existence of poor children” as the Third World criteria, the USA is a Third World country, too. In fact, there are probably many more poor children here than in Romania. :)
But I hope they don’t need to spend their lives on rubbish dumps.
I’m pretty sure there are those who do.