That is a very pious affirmation. Holy Mother Church only operates under the mercy of God. Since she is not underground in America as she must be in China, she functions within the corporate and legal structures of the nation and is permitted to function by the State as an untaxed entity through her several apostolates, orders, and ministries. As long as she is 'above ground' and functioning within the legal and governmental system of the United States her resources and fuctions are not sovereign.
19. The Church is not a true and perfect society, entirely free- nor is she endowed with proper and perpetual rights of her own, conferred upon her by her Divine Founder; but it appertains to the civil power to define what are the rights of the Church, and the limits within which she may exercise those rights.—Allocution "Singulari quadam," Dec. 9, 1854, etc.20. The ecclesiastical power ought not to exercise its authority without the permission and assent of the civil government.—Allocution "Meminit unusquisque," Sept. 30, 1861.
24. The Church has not the power of using force, nor has she any temporal power, direct or indirect.—Apostolic Letter "Ad Apostolicae," Aug. 22, 1851.
30. The immunity of the Church and of ecclesiastical persons derived its origin from civil law.—Damnatio "Multiplices inter," June 10, 1851.
31. The ecclesiastical forum or tribunal for the temporal causes, whether civil or criminal, of clerics, ought by all means to be abolished, even without consulting and against the protest of the Holy See.—Allocution "Nunquam fore," Dec. 15, 1856; Allocution "Acerbissimum," Sept. 27, 1852. (Bl. Pius IX, Syllabus of Modern Errors)