What would be an example of an act that involves patriotism but not nationalism?
According to Wikipedia, the definition of patriotism is:
Patriotism is an emotional attachment to a nation which an individual recognizes as their homeland. This attachment, also known as national feeling or national pride, can be viewed in terms of different features relating to one's own nation, including ethnic, cultural, political or historical aspects.
Whereas nationalism is:
Nationalism is oriented towards the development and maintenance of a common communal identity based on shared characteristics typically including culture, language, religion, political goals and/or a belief in a common ancestry.
In some texts I've read, patriotism is regarded as something "good" (love for your nation), whereas nationalism can be seen as something "bad" (the nation I belong to is somehow better than the other ones). But for me, this difference is very subtle, because in both cases the main feature that pins the concept down is that you are "emotionally attached" to your nation (or better, to what you consider your nation) as well as to all the things that it stands for: culture, moral values, religion, language, etc.
I'll try to set an example. What if I live in a country in which some region decides unilaterally (for instance via a referendum just in that region), to split from the rest of the country? In this case, I could decide to take sides against the secessionists because I would consider such declaration as an agression to my homeland and nation (patriotism) but also against the common national identity (nationalism) of the "main" country. In this case, I would be imposing my own view of what I consider my "homeland" and associated cultural values (patriotism) to many people who don't necessarily share that opinion and also, I would be imposing my way of living and culture (nationalism) over the secessionists.
What I'm trying to say with this example is that in a lot of situations, both feelings are totally equivalent to me and I find it difficult to think about a situation of an act that is motivated just by patriotism and not by nationalism. Therefore, I always have the feeling that both terms are somehow interchangeable.