I'm a home cook and also love cakes and pastry baking, and I've had the problem that most of my friends love my cakes and want the recipe, but i have had to convert them into grams.
Now, one thing you MIGHT be able to do is find an american measuring cup somewhere. That makes it all easy.
The second thing you can do is measure something easy and constant by weight knowing the cup equivalent, and then mark a measuring cup yourself with cup marks.
You probably can find those measuring cups they sell in europe that have grams for flour, sugar, water, oil, etc, all marked off in different scales. You could add your own scratching into it or writing the marks on a cardboard strip that you attach each time to the cup.
Or you can use these equivalences that I use (below). Keep in mind that while sugar is pretty constant, flour is not. Whatever anyone tells you, flour measuring is not going to EVER be perfect, because flour is a biological product, made from grain, which varies depending on the weather, the climate, the growing conditions, from place to place and from year to year. Some flour will absorb more and some less. But for home cooking, these small variations are not so relevant. I don;t know about the flour in Holland, but in Italy, the flour is 0 or 00. The 00 is finer, and is ok when the recipe calls for "cake flour" but is definitely too "weak" if used where the recipe calls for "flour" or All Purpose (or AP) flour. In that case, you will need to add a significant amount more of this 00 flour. Roughly I find about two tablespoons per cup. I also reduce the butter a little. Otherwise cookies, piecrusts and even cakes will be greasy and flat. Giving a perfect equivalence with flour is also difficult because if you pour it into the cup and let it settle a little it might be more packed and if you sift it into the cup it will be less packed, and if you scoop it int the cup it will probably be even more packed than pouring. Again, I bake all the time and my stuff comes out ok, and i am not all that precise.
The 0 flour is more similar, but still made of softer wheat than american flour is (Americans do a lot of bread baking and so all purpose flour is "stronger", that is, produces more gluten.)
This is the chart I use. I can bake with these equivalences, and the stuff comes out good. Keep in mind, though, that i haven't factored in the difference in flour type,.so if dutch flour is like italian (and I believe, french) you will need to use more.
sugar and butter have the same mass so the grams are the same per cup - sticks refers to the form american butter comes in, and some recipes use sticks as a measure.
SUGAR AND BUTTER (AND LIQUIDS)
1/4 cup = 4 tbsp = 1/2 stick = 50 gm
1/3 cup = 5 1/3 tbsp = 60 gm
6 tbsp = 75 gm
1/2 cup = 8 tbsp = 1 stick = 100 gm
2/3 cup = 10 2/3 tbsp = 135 gm
1 cup = 16 tbsp = 2 sticks = 200 gm
1 cup = 140 gm
1/2 cup = 70 gm
1/4 cup = 35 gm
1/3 cup = 47 gm
3/4 cup = 105 gm
And if you cam't find unsweetened chocolate in Holland, you can use cocoa and butter to substitute in this proportion. (Keep in mind that what europeans consider bitter chocolate is sweetened. Unsweetened chocolate is really inedible on its own. So if you can eat it it's probably not american baking chocolate). Chocolate in recipes is usually measured in "squares" (ounces, i believe)
for each square of bitter chocolate use 3 tbsp cocoa plus one additional tbsp butter added with the butter.
Hope this helps.